Laser technology is applied for a large variety of material processing tasks, such as cutting, drilling, welding, marking, engraving and material ablation. Nearly all materials can be processed, e.g. metals, metal alloys, ceramics, diamonds, synthetic diamonds, carbon fibres, sapphire, quartz, glass, plastics and more. In almost every case, the laser light is focused into a very small spot onto the work piece using a focusing lens, to enable the processing task by generating sufficient energy on the work piece. The work piece therefore has to be precisely aligned into the laser focus throughout the processing task.
Liquid-jet guided laser technology, as for example described in patent EP 1940579B1 and U.S. Pat. No. 8,859,988B1, which are hereby incorporated by reference in their entirety for all purposes, couples the laser focus into a small liquid-jet, for example, through a focusing lens. This coupling takes place in a coupling unit. The coupling unit can include a metal chamber that on the side of the focusing lens is closed with a laser protection window. On the opposite side the chamber carries a nozzle. Liquid provided to the coupling unit flows between window and nozzle and leaves the nozzle in form of a liquid-jet. The energy of the laser spot in the focal plane is captured inside the liquid-jet and guided to the work piece through internal reflection. This method eliminates the necessity to control the distance of the work piece precisely because the required energy to perform the processing is available throughout the laminar length of the liquid-jet. Any liquid that provides suitable light guide capabilities can be used to form the liquid-jet.
There is a need for improving the liquid-jet laser technology, for example, to allow ease of servicing the laser protection window and the nozzle.